Method and compositions for cleaning ovens and the like

ABSTRACT

A COMPOISITION FOR THE PRE-TREATMENT OF SURFACES WHICH ARE SUBJECTED TO HEAT AND LIABLE TO SOILING BY BAKED ON ORGANIC DEPOSITS COMPRISING A HYDROLYZING AMOUNT OF AN ALKALI METAL BICARBONATE, AN AQUEOUS VEHICLE THEREFOR AND A SURFACE ACTIVE AGENT.

United States Patent O 3,827,983 METHOD AND COMPOSITIONS FOR CLEANING OVENS AND THE LIKE Harry Ian Mitchell, Rochdale, and Kenneth Tomlinson, Bramhall, England, assignors to Colgate-Palmolive Company, New York, N.Y.

No Drawing. Original application July 30, 1970, Ser. No. 59,753, now Patent No. 3,679,993. Divided and this application June 7, 1972, Ser. No. 260,700 The portion of the term of the patent subsequent to June 27, 1989, has been disclaimed Int. Cl. C11d 9/12 US. Cl. 25289 16 Claims ABSTRACT OF THE DISCLOSURE A composition for the pre-treatment of surfaces which are subjected to heat and liable to soiling by baked on organic deposits comprising a hydrolyzing amount of an alkali metal bicarbonate, an aqueous vehicle therefor and a surface active agent.

This is a division of application Ser. No. 59,753 filed July 30, 1970.

This invention relates to the cleaning of surfaces, such as the surfaces of ovens, which are subjected to heat and are liable to soiling by baked-on organic deposits. The soiling matter deposited on ovens, such as domestic cooker ovens, consists of a complex organic mixture of natural fats and other deposits from the cooking of food. When heated at normal oven temperatures, this soiling matter is converted into an infusible polymeric mass in which part of the organic material may also be charred.

Detergents, scouring powders and similar cleansing products, even when alkaline (e.g. those containing phosphates), although highly efficient for removing normal greasy soiling matter, are not usually adequate for removing baked-on soil of the type found in ovens.

The removal of this type of soil is therefore a considerable problem, requiring powerful chemical or physical action. Among the most effective chemical compounds known for this purpose are the caustic alkalis, sodium and potassium hydroxides. Their mode of action is that they react with and hydrolyse natural fats, thus converting them at least partially into their sodium or potassium salts, which are water-soluble and thus easily removed. Commercial products of this type usually contain up to 3% of sodium hydroxide together with other components such as solvents and emulsifiers which promote the efliciency of the product. They may be applied directly by brush or sponge, or more conveniently by means of an aerosol spray. Products of this type, although efficient in their action, suifer from a number of major disadvantages. The most important disadvantage is the serious hazard to the eyes and skin arising from the use of caustic alkalis. If inadvertently sprayed in the eyes, a product of this type could cause permanent blindness. It is also common practice for housewives to use rubber gloves when applying a product of this type of avoid damage to the skin. Such products may also damage adjacent surfaces, such as paint, aluminum or wood, onto which they may be inadvertently sprayed. Another disadvantage is that such products when applied to soiled oven surfaces must attack the soiling matter from the outer surface, while the most severe charring and polymerization is generally present in the interior of the soil layer, adjacent to the oven wall. This makes cleaning more difiicult.

Alkalis less alkaline than caustic soda, although they would avoid some of the hazards already indicated, are not very effective in hydrolyzing baked-on fat in the short time of application, and consequently are not eflicient oven cleaners.

3,827,983 Patented Aug. 6, 1974 Certain pre-treatment preparations are known which act by forming a physical barrier between the oven wall and the soiling matter, and do not depend on chemical actions. Those preparations are expensive and not very effective.

It is an object of this invention to avoid the disadvantages of the known oven cleaner preparations, and at the same time to provide a simple and etfective procedure for oven cleaning.

According to one aspect of the invention a method of cleaning a surface which is subjected to heat and is liable to soiling by baked-on organic deposits comprises apply ing to the clean surface an alkali metal bicarbonate, and washing the surface clean again after such soiling.

According to other aspects of the invention there are provided various compositions for the pre-treatment of such a surface and comprising an alkali metal bicarbonate, an aqueous vehicle and other components as hereinafter described.

According to a further aspect of the invention there is provided a pressurized aerosol-type dispenser containing a solution or suspension of an alkali metal bicarbonate and a propellant.

The principle of the invention is as follows: Alkali metal bicarbonates, which are very mild alkalis, decompose on moderate heating to form the corresponding carbonates which are much stronger alkalis. These carbomates in turn are sufliciently powerful to promote the slow hydrolysis of fats, particularly under the influence of temperature. After application of the alkali metal bicarbonate to the clean oven surface, use of the oven converts it to the corresponding carbonate, which slowly hydrolyses fats deposited on the walls, thereby converting them at least partially into the corresponding soaps which are easily removed with warm water.

Alkali metal bicarbonates are very mild alkalis which cannot harm the eyes or the skin. They are harmless to painted surfaces, aluminium and wood, all of which may be damaged by caustic alkalis. Since the product is applied directly on the clean oven walls, it acts first on the fat which is first deposited and is therefore most likely to polymerize and char and be the most intractable.

Oven pre-treatments according to the invention can be etfected in a variety of ways, the following being typical examples:

(a) Application of a solution or suspension of alkali metal bicarbonate by means of a sponge, brush or cloth.

(b) Application of a solution or suspension of alkali metal bicarbonate by means of a hand operated spray bottle or a hand pump or automatically (e.g., byventure action) by means of a cartridge of compressed gas.

(0) Application of a gel or paste composition containing alkali metal bicarbonate.

(d) Application of a solution or suspension of alkali metal bicarbonate by means of an aerosol type pressurized dispenser.

The ways (b) and (d) are preferred.

Examples of suitable alkali metal bicarbonate are sodium bicarbonate, potassium bicarbonate and mixtures thereof.

The basic material is a solution or suspension of'.t.he alkali metal bicarbonate in water. For a solution -the amount present is governed by the solubility of the particular salt in water. Typical approximate figures are: sodium bicarbonate, 8% at 20 C.; potassium bicarbonate, 25% at 20 C. These and all other percentages are by weight. 7

On the grounds of cost, sodium bicarbonate is preferred, and a solution of 4% to 7% is sufiicient to give adequate performance. It is possible to produce a stronger material by including additional alkali metal bicarbonate in a suspended form.

Other materials may be added for imparting desired additional properties. Examples are:

(i) Surface-active agents Ethoxylated nonyl phenols (especially 81l mols ethylene oxide),

Phosphate ester (e.g. Solumin PFN 95 manufactured by Glovers Chemicals Ltd. of England),

Sodium dodecylbenzene sulphonate.

Combinations of various surface-active agents can be used, and the addition of a hydrotrope (e.g. sodium xylene sulphonate) may improve their performance. The amount of surface-active agent used can vary within wide limits, but normally a concentration of about 0.5% of surfaceactive agent (including the hydrotrope, if present) is sufiicient.

(ii) suspending agents These are only necessary when excess of an alkali metal bicarbonate is present in suspended form. A satis factory sp'spending agent is a low density hydrated silica powder,- e.g. Aerosil 200 in an amount of about 1%.

(iii) Corrosion inhibitors These may be included to inhibit corrosion of the aerosol can and oven walls. Examples are sodium benzoate, sodium nitrite and mixtures thereof.

(iv) Coloring materials A coloring material such as a dye or pigment may be adde to afford a visual contrast between the oven wall and the applied composition to facilitate uniform and complete application, or merely to alter the appearance of the resulting dried film which in the absence of added color has a whitish hue.

(v) Gelling or thickening agents Materials such as carboxymethyl cellulose may be added to gel or thicken compositions of the type above.

(vi) -Propellants addition details are given for the application of the same base by means of an aerosol dispenser.

4 EXAMPLE 1 Base formula: Percent Sodium bicarbonate 7. Nonyl phenol polyethoxylate (8-9 ethylene oxides) e.g. Ethylan TU (Lankro Chemicals Ltd., England) 1.5 Sodium Xylene sulphonate (30% aqueous solution) 1.5 Water 90.

For filling into an aerosol dispenser the following weights are used:

Percent Base as above 90. Difiuorodichloromethane 5. Tetrafluorodichloroethane 5.

100.0 EXAMPLE 11 Base formula: Percent Potassium bicarbonate 15.00 Sodium salt of disulphonated dodecyldiphenyloxide (45% aqueous solution) (Dowfax 2A1) 0.4

Nonylphenol polyethoxylate (8-9 ethylene oxides) e.g. Ethylan TU (Lankro Chemicals Ltd.) 0.15 Water 84.45

For filling into an aerosol dispenser the following Weights are used:

Sodium salt of disulphonated dodecyldiphenyloxide 45% (Dowfax 2A1) 1.0 Water 82.0

For filling into an aerosol dispenser the following weights are used:

Percent Base as above 80.0

Difluorodichloromethane 10.0

Tetrafluorodichloroethane 10.0

Products manufactured according to the examples were evaluated by the procedure described below.

Enameled metal plates 18" x 10" were heated to C. in an oven. The hot plates were removed from the oven and a mask was placed over one half of each plate. The uncovered half of each plate was then treated with the product under test. After drying the plates the whole area was coated evenly with a layer of greasy soiling matter (deep frying cooking fat, lard and tallow were used as typical soiling materials). The plates were then heated in an oven for at least 2.4 hours at temperatures between 200 and 250 C. After removal from the oven the plates were cooled. The whole surface of the plates was then washed with a /2% solution of soap in warm water applied by a sponge. The burnt-on soiling matter was completely removed from the treated areas without difiiculty. The untreated areas were still heavily soiled with burnt-on fat after the treatment.

What is claimed is:

1. A composition for the pre-treatment of surfaces which are subjected to heat and liable to soiling by baked on organic deposits consisting essentially of at least about 4% of an alkali metal bicarbonate which decomposes under the influence of heat to the corresponding carbonate, an aqueous vehicle therefore and an eifective amount of a surface-active agent.

2. A composition as claimed in claim 1. in which the alkali metal bicarbonate is in solution in the aqueous vehicle.

3. A composition for the pre-treatment of surfaces which are subjected to heat and liable to soiling by baked on organic deposits consisting essentially of at least about 4% of an alkali metal bicarbonate an effective amount of a suspending agent, said bicarbonate being in suspension in an aqueous vehicle and which decomposes under the influence of heat to the corresponding carbonate.

4. A composition in gel form for the pre-treatment of surfaces which are subjected to heat and liable to soiling by baked on organic deposits consisting essentially of at least about 4% of an alkali metal bicarbonate which decomposes under the influence of heat to the corresponding carbonate, an effective amount of an aqueous vehicle therefor and a gelling agent.

5. A pressurized aerosol-type dispenser containing an aqueous solution or suspension of an alkali metal bicarbonate and a pressurizing amount of a propellant.

6. A composition as defined in claim 1 wherein said alkali metal bicarbonate is selected from the group consisting of sodium and potassium bicarbonates and mixtures thereof.

7. A composition as defined in claim 1 wherein said surface active agent is included in amounts of up to about 1.5% by weight.

8. A composition as defined in claim 1 wherein said surface active agent is selected from the group consisting of ethoxylated nonyl phenols, phosphate esters and sodium dodecylbenzene sulfonates.

9. A composition as defined in claim 3 wherein said alkali metal bicarbonate is selected from the group consisting of sodium and potassium bicarbonates and mixtures thereof.

10. A composition as defined in claim 3 wherein said suspending agent is included in amounts of about 1% by Weight.

1.1. A composition as defined in claim 3 wherein said suspending agent is hydrated silica.

12. A composition as defined in claim 4 wherein said alkali metal bicarbonate is selected from the group consisting of sodium and potassium bicarbonates and mixtures thereof.

13. A composition as defined in claim 4 wherein said gelling agent is carboxymethyl cellulose.

14. A composition as defined in claim 12 wherein said sodium bicarbonate is included in amounts of about 4 to about 7% by weight.

15. A composition as defined in claim 1 wherein said aqueous vehicle is water.

16. A composition as defined in claim 1 wherein said surface active agent is selected from the group consisting of ethoxylated nonyl phenols, phosphate esters, sodium dodecyl benzene sulfonate, combinations thereof and mixtures thereof with a hydrotrope.

References Cited UNITED STATES PATENTS 3,183,110 5/1965 Aler et al. 252-89 3,198,747 8/1965 Cook et al 25215 6 3,296,147 l/l967 Gatza 252156 3,303,052 2/1967 Hatch et al 1176 3,658,711 4/1972 Mukai et a1 252-90 FOREIGN PATENTS 751,361 1/1967 Canada 252156 WILLIAM E. SCHULZ, Primary Examiner US. Cl. X.R. 

